This invention relates in general to electrostatic fluidized bed apparatus and deals more particularly with improved apparatus for coating articles by the electrostatic deposition of particulate material.
The advantages of electrostatic powder coating are well known and apparatus of the type in general use for the application of such coating usually comprises some form of permanent or semipermanent installation which requires external supporting equipment, which may, for example, comprise an air compressor, or high voltage electrical source connected to the equipment by plumbing or electrical lines. Such equipment is particularly well suited for use where a single coating material is to be applied to a relatively large volume of work. However, when the coating material is changed, it is generally necessary to shut down the equipment and thoroughly clean the fluidizing bed so that the material to be used in the next production run will not be contaminated by material used in the previous run. Further, if the equipment is of a type which employs exposed electrodes, a relatively large quantity of powdered coating material must be used even though the fluidizing bed may be relatively small, since it is usually necessary that the coating material cover the electrodes to assure efficient operation. In such an installation the electrodes must also be cleaned whenever the coating material is changed to avoid risk of contamination. The resulting down time is costly and tends to offset advantages derived from the use of such equipment in short run production. Consequently, such apparatus has not realized its full potential for use in the short run production of articles requiring coatings of differing colors or materials or for laboratory use. The present invention is concerned with the aforedescribed problems.